Not to dispute your main point here (that emotionally-protected false beliefs discourage contact with reality), but do you really think that many religious practices were developed consciously and explicitly for the purpose of preventing contact with outside ideas? It seems to me that something like kosher law was more likely the combination of traditional practice and the desire to forge a sense of social identity than a structure explicitly designed to stop interactions. Group differences hinder interaction between groups, but that doesn't mean that the purpose of group differences is to do so.

I don't disagree with you on the point that religion often explicitly discourages contact with nonbelievers, either, but that seems to me to be more easily explained by honest belief than Dark Side practices. If you believe something is true (and important to know the truth of) but that someone can be easily persuaded otherwise by sophistic arguments, then it's reasonable to try to prevent them from hearing them. If someone believes in global warming but doesn't have a firm grasp on the science, then you shouldn't let them wander into a skeptics' convention if you value valid beliefs.